Production method and production device for thin film

ABSTRACT

An electron beam evaporation source ( 42 ) that contains a first thin film material, an electron beam source ( 44 ) that emits an electron beam ( 45 ) to be used to evaporate the first thin film material by heating, and a resistance heating evaporation source ( 48 ) for evaporating a second thin film material by heating using a resistance heating method are arranged so that the electron beam ( 45 ) passes through a vapor stream of the second thin film material. Thus, evaporated atoms of the second thin film material can be ionized. As a result, a thin film having improved properties and increased mechanical strength can be formed. Further, since it is no longer necessary to use another device for ionizing the evaporated atoms of the second thin film material, the complication of a configuration and a cost increase can be prevented.

TECHNICAL FIELD

The present invention relates to a method and apparatus formanufacturing a thin film.

BACKGROUND ART

As the age of information and communication progresses, thin films havebeen finding wider application. With this as a background, developmentsalso have been made rapidly in the composition of a thin film and theprocesses for manufacturing a thin film on a daily basis.

As a representative process for manufacturing a thin film, a vapordeposition method has been known. Among the widely used vapor depositionmethods for heating evaporation materials are a resistance heatingmethod and an electron beam heating method.

Meanwhile, a thin film can be provided with various properties bysimultaneously evaporating various kinds of materials from differentevaporation sources and allowing them to adhere to a common area to bevapor-deposited. In this manner, a thin film having a desiredcomposition can be formed (see, for example, JP 1(1989)-117208 A). Inthis case, as one possible method for heating the materials, all of thematerials are heated by the resistance heating method. As anotherpossible method for heating the materials, all of the materials areheated by the electron beam heating method. As still another possiblemethod for heating the materials, the resistance heating method and theelectron beam heating method are performed in combination.

Generally, the electron beam heating method requires greater cost andlarger-scale equipment. In contrast to this, the resistance heatingmethod is more convenient and cost-effective, thereby achievingexcellent mass productivity in the industrial field. Thus, in manycases, combined methods including the resistance heating method havebeen used.

However, while in the resistance heating method, evaporated atomsresulting from heating a vapor-deposition material are only allowed toadhere on a surface to be vapor-deposited, in the electron beam heatingmethod, evaporated atoms resulting from heating are ionized to beactivated by an electron beam. Therefore, a thin film obtained by theelectron beam heating method exhibits excellent properties in terms ofthe size of a crystal and the density compared with a thin film obtainedby the resistance heating method. Thus, when forming a thin film made ofvarious kinds of materials, the combined methods including theresistance heating method have presented a problem of, for example, adecrease in the mechanical strength of the obtained thin film.

DISCLOSURE OF THE INVENTION

The present invention has as its object to provide a method andapparatus for manufacturing a thin film that can solve theabove-mentioned problem caused by the use of the resistance heatingmethod and improve the mechanical strength of a thin film simply andcost-effectively. In the method and apparatus according to the presentinvention, a thin film containing a first thin film material and asecond thin film material is formed in such a manner that the first thinfilm material and the second thin film material are evaporated byheating using the electron beam heating method and the resistanceheating method, respectively.

In order to achieve the above-mentioned object, the present inventionhas the following configuration.

A method for manufacturing a thin film according to the presentinvention is a method for manufacturing a thin film containing a firstthin film material and a second thin film material on a surface to bevapor-deposited by vacuum vapor deposition. In the method, the firstthin film material and the second thin film material are evaporated byheating using an electron beam heating method and a resistance heatingmethod, respectively, and an electron beam to be used to heat the firstthin film material is passed through a vapor stream of the second thinfilm material.

Furthermore, an apparatus for manufacturing a thin film according to thepresent invention includes an electron beam evaporation source that isarranged so as to face a surface to be vapor-deposited and contains afirst thin film material, an electron beam source that emits an electronbeam to be used to evaporate the first thin film material by heatingusing an electron beam heating method, and a resistance heatingevaporation source that is arranged so as to face the surface to bevapor-deposited and evaporates a second thin film material by heatingusing a resistance heating method. In the apparatus, the electron beamevaporation source, the electron beam source and the resistance heatingevaporation source are arranged so that the electron beam passes througha vapor stream of the second thin film material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of an embodimentof an apparatus for manufacturing a thin film according to the presentinvention.

FIG. 2 is a schematic diagram showing a configuration of an apparatusfor manufacturing a thin film according to comparative examples.

BEST MODE FOR CARRYING OUT THE INVENTION

According to the above-described method and apparatus for manufacturinga thin film according to the present invention, an electron beam to beused to heat the first thin film material passes through a vapor streamresulting from evaporating the second thin film material by heatingusing the resistance heating method, thereby allowing evaporated atomsof the second thin film material to be ionized. As a result, a thin filmhaving improved properties and increased mechanical strength can beformed. Further, it is no longer necessary to use another device forionizing the evaporated atoms of the second thin film material, therebysimplifying the configuration and reducing costs.

Hereinafter, the present invention will be described in detail withreference to the appended drawings.

FIG. 1 is a schematic diagram showing a configuration of an embodimentof an apparatus for manufacturing a thin film according to the presentinvention.

A long belt-shaped supporting base 20 unwound from an unwinding roll 12passes along an unwinding side guide roll 14 and is conveyed along anouter peripheral face of a cylindrical can roller 10 that is rotated ina direction indicated by an arrow. Then, the supporting base 20 passesalong a winding side guide roll 16 and is wound by a winding roll 18.

Below the can roller 10, an electron beam evaporation source 42 thatcontains a first thin film material used for forming a thin film, aresistance heating evaporation source 48 for evaporating a second thinfilm material by heating using the resistance heating method, and anelectron beam source 44 that emits an electron beam 45 to be used toevaporate the first thin film material in the electron beam evaporationsource 42 by heating using the electron beam heating method, arearranged in this order. In practical use, it may be necessary to useother devices such as a magnetic field application device for allowingthe electron beam 45 from the electron beam source 44 to impinge on thefirst thin film material in the electron beam evaporation source 42,which are not shown.

Reference numerals 30 and 32 denote a vacuum container and a partitionwall dividing an inner portion of the vacuum container 30, respectively.Further, reference numerals 34 and 36 denote an opening that is providedin the partition wall 32 so that a lower portion of the can roller 10can be exposed and a vacuum pump for maintaining the inside of thevacuum container 30 at a predetermined degree of vacuum, respectively.Further, reference numerals 38 and 39 denote a gas nozzle forintroducing a reactive gas into an evaporated atom stream and a biasdevice that applies a bias voltage to the winding side guide roll 16,respectively.

The description is directed next to an operation of the apparatus formanufacturing a thin film according to the present invention with theabove-described configuration.

While the supporting base 20 is conveyed along the can roller 10, thefirst thin film material in the electron beam evaporation source 42 andthe second thin film material in the resistance heating evaporationsource 48 are evaporated by heating, respectively. As a result,evaporated atoms of the first thin film material and evaporated atoms ofthe second thin film material are allowed to adhere on the supportingbase 20 exposed inside the opening 34, thereby allowing a thin film madeof the first thin film material and the second thin film material to beformed.

In the present invention, the electron beam evaporation source 42 andthe electron beam source 44 are arranged so as to interpose theresistance heating evaporation source 48 between them. Therefore, theelectron beam 45 from the electron beam source 44 sequentially passesthrough a vapor stream of the second thin film material emitted from theresistance heating evaporation source 48 and a vapor stream of the firstthin film material emitted from the electron beam evaporation source 42.This allows both of evaporated atoms of the second thin film materialand evaporated atoms of the first thin film material to be ionized. Asdescribed above, in the present invention, evaporated atoms of thesecond thin film material from the resistance heating evaporation source48 also can be ionized. Conventionally, such evaporated atoms are notionized. As a result, a thin film having improved properties can beformed. For example, the mechanical strength of the thin film can beincreased.

As long as the electron beam evaporation source 42, the electron beamsource 44 and the resistance heating evaporation source 48 are arrangedso that the electron beam 45 passes though a vapor stream of the secondthin film material from the resistance heating evaporation source 48,the arrangement of these elements is not limited to the arrangementshown in FIG. 1. It is preferable that as shown in FIG. 1, the electronbeam evaporation source 42, the electron beam source 44 and theresistance heating evaporation source 48 are arranged substantially onthe same plane for the following reason. That is, this arrangement makesit easier to allow the electron beam 45 to pass through a vapor streamof the first thin film material and a vapor stream of the second thinfilm material.

There is no particular limit to the first and second thin filmmaterials. For example, the first and second thin film materials can bemade of Li, Co, Mn, P, Cr or the like. A thin film that can be formedhas a composition represented by, for example, LiCoO₂, LiPON or thelike. For example, Co can be used for the first thin film material, andLi can be used for the second thin film material.

The supporting base 20 is formed, for example, of metal foil or a resinsheet. The metal foil can be formed of foil made of stainless steel,copper, nickel or the like. The resin sheet can be formed of a sheetmade of, for example, polyethylene terephthalate.

Further, in the case of using metal or the like as the thin filmmaterials, it is preferable that in forming a thin film, a negativevoltage (bias voltage) is applied to the winding side guide roll 16 byusing the bias device 39. The winding side guide roll 16 is in contactwith a surface of the supporting base 20 on a side on which the thinfilm is formed. Accordingly, the same negative bias voltage also isapplied to a surface to be vapor-deposited of the supporting base 20inside the opening 34 through the thin film having conductivity. As aresult, an ion (for example, a metal ion) originating in an evaporatedatom ionized by the electron beam 45 is allowed to adhere to the surfaceto be vapor-deposited in a high-energy state. Thus, a thin film that isimproved in strength, density, crystallinity and the like can be formed.As long as a bias voltage can be applied to the surface to bevapor-deposited, a means for applying the voltage is not limited to theconfiguration shown in FIG. 1. For example, it also may be possible toapply a bias voltage to the can roller 10. Alternatively, it also may bepossible to use a conductive material for the supporting base 20 andapply a bias voltage to this supporting base 20. Further, the polarityof a bias voltage is only required to be reverse to the polarity of theevaporated atom that has been ionized and is not limited to the negativepolarity as described above.

Furthermore, when forming a thin film, it is possible to performreactive vapor deposition by introducing a reactive gas from the gasnozzle 38 toward an area on which the thin film is to be formed. In thepresent invention, evaporated atoms of the second thin film materialfrom the resistance heating evaporation source 48 also are ionized,thereby allowing the reaction with a reactive gas to be improved. Thereis no particular limit to the material of the reactive gas, and oxygen,nitrogen or the like can be used.

EXAMPLES (Example 1)

Using the manufacturing apparatus shown in FIG. 1, a Ni—Cr thin film wasformed on the supporting base 20 in the following manner.

That is, as the supporting base 20, a polyethylene terephthalate film of20 μm thickness was allowed to travel along the water-cooled can roller10. Cr in the electron beam evaporation source 42 was heated by theelectron beam 45 from the electron beam source 44, and Ni in theresistance heating evaporation source 48 was subjected to resistanceheating. In this case, a reactive gas was not supplied from the gasnozzle 38, and a bias voltage was not applied by the bias device 39.

In the above-described manner, the Ni—Cr thin film of 5 μm thicknesscontaining 80% Ni and 20% Cr was formed on the supporting base 20.

(Comparative Example 1)

Using a manufacturing apparatus shown in FIG. 2, a Ni—Cr thin film wasformed on the supporting base 20. The apparatus shown in FIG. 2 has thesame configuration as that of the apparatus shown in FIG. 1 except thatthe arrangement of the electron beam evaporation source 42, the electronbeam source 44 and the resistance heating evaporation source 48 isdifferent. In FIG. 2, like reference numerals indicate like constituentelements that are the same as those shown in FIG. 1, for which duplicatedescriptions are omitted. In the apparatus shown in FIG. 2, an electronbeam 45 from an electron beam source 44 reaches an electron beamevaporation source 42 without passing through a vapor stream of a thinfilm material from a resistance heating evaporation source 48.Accordingly, evaporated atoms from the resistance heating evaporationsource 48 never can be ionized.

Using an apparatus having the above-described configuration, a Ni—Crthin film of 5 μm thickness containing 80% Ni and 20% Cr was formed on asupporting base 20 under exactly the same conditions as those in thecase of Example 1.

[Evaluation]

With respect to each of the thin films of Example 1 and ComparativeExample 1, the peel strength was determined.

The determination was made in the following manner. That is, each thinfilm was incised in the form of a grid with a pitch of 2 mm by using arazor. Then, an adhesive tape (“Scotch Mending Tape”, a trademark ofSumitomo 3M Limited) was attached to each thin film and was subsequentlypeeled slowly. At this time, the number of pieces of each thin filmpeeled from the supporting base 20 (assuming that the parameter was 100)was determined.

As a result, while the number of peeled pieces of Example 1 was 13, inthe case of Comparative Example 1, the number was 45.

Conceivably, in Example 1, Ni atoms evaporated by the resistance heatingmethod were ionized by an electron beam, and thus the improved peelstrength was attained.

(Example 2)

Using the manufacturing apparatus shown in FIG. 1, a LiCo—O thin filmwas formed on the supporting base 20 in the following manner.

That is, as the supporting base 20, a stainless steel sheet of 10 μmthickness was allowed to travel along the water-cooled can roller 10.While Co in the electron beam evaporation source 42 was heated by theelectron beam 45 from the electron beam source 44, Li in the resistanceheating evaporation source 48 was subjected to resistance heating. Vapordeposition was performed by supplying an oxygen gas from the gas nozzle38. A bias voltage was not applied by the bias device 39.

In the above-described manner, the LiCo—O thin film of 2 μm thicknesscontaining Co and Li at a ratio of 1 to 1 was formed on the supportingbase 20.

(Comparative Example 2)

Using the manufacturing apparatus shown in FIG. 2, a LiCo—O thin film of2 μm thickness containing Co and Li at a ratio of 1 to 1 was formed onthe supporting base 20 under exactly the same conditions as those in thecase of Example 2.

[Evaluation]

With respect to each of the thin films of Example 2 and ComparativeExample 2, the scratch strength was determined.

The determination was made in the following manner. That is, thesupporting base on which a thin film was formed was fixed on a levelsurface, and under a load, a stylus having a radius of 15 μm was broughtinto contact with the thin film. The stylus was allowed to oscillate atan amplitude of 10 μm and a frequency of 30 Hz. The load to be appliedto the stylus was increased gradually, and a load with which a breakingflaw was caused in the thin film was determined as the scratch strength.

As a result, while Example 2 had a value represented by 0.49×10⁻³N (5gf), Comparative Example 2 had a value represented by 0.20×10⁻³N (2 gf).

In Example 2, conceivably, Li atoms evaporated by the resistance heatingmethod were ionized by an electron beam, and thus the improved scratchstrength was attained.

The embodiments disclosed in this application are intended to illustratethe technical aspects of the invention and not to limit the inventionthereto. The invention may be embodied in other forms without departingfrom the spirit and the scope of the invention as indicated by theappended claims and is to be broadly construed.

For example, although in each of the examples described above, thepresent invention was applied to continuous winding vapor deposition inwhich the surface to be vapor-deposited was formed of a travelingsubstrate in the shape of a long film, the present invention is notlimited thereto. The surface to be vapor-deposited also may be formedof, for example, a traveling substrate in the shape of a sheet or astationary substrate. The substrate can be formed of a polymer materialor a material such as metal, semimetal, glass, ceramic or the like, andfurther can be formed of a composite material of these materials.

When forming a thin film, it also is possible to use the elements incombination with other elements such as an ion generating source and anelectron generating source. For example, an ion gun, a plasma gun andother forms of electron guns can be used. Further, when forming a thinfilm, it also may be possible to perform ultraviolet or infraredirradiation, or irradiation by using various kinds of lasers such as acarbonic acid gas laser, a YAG laser, an excimer laser, and asemiconductor laser. By performing such irradiation, an evaporationmaterial can be improved in an ionization rate, reactivity, adhesion toa film and the like, and the crystallinity of the evaporation materialand a surface property of a film and the like can be controlled.

The application of a bias voltage also is not limited to that in theexamples described above. A bias voltage to be applied can be a directvoltage, an alternating voltage or a combination of these voltages, andbias voltages having various waveforms and voltage values can be used.This allows thin films to be formed so as to have properties varying ina thickness direction. A bias voltage to be applied also may be adjustedby controlling not only a voltage value but also a current value, whichis particularly useful with respect to variations of an evaporationsource.

In the resistance heating method, heating also may be performed by theuse of a heater, a lamp or a boat, or by the induction heating or thelike. In the electron beam heating method, an electron gun having adeflection angle of 90 degrees, 180 degrees, 270 degrees or the like andan axial electron gun can be used. When an ion plating method in whichiron excitation caused by induction is applied to the resistance heatingmethod is used in combination with the electron beam heating methodaccording to the present invention, an ionization rate can be increased,and thus it is possible to achieve various forms of improvements inproperties and advantages in terms of production.

As for a method of producing a vacuum, as long as the method can attainthe degree of vacuum at which vapor deposition using electron beams canbe performed, various methods and combinations of those methods can beused. For example, vacuum can be produced by the use of a cryopump, anoil diffusion pump, a turbo pump, an ion pump or the like. However, thepresent invention is not limited to the use of these pumps.

In most cases, the introduction of a gas enhances the effect of thepresent invention and in no cases, causes the effect to be deteriorated.

Furthermore, in the present invention, it is possible to monitor anevaporation state. Since an evaporation material is ionized, anevaporation state of the material can be monitored by an optical meansutilizing plasma light emission. It is particularly useful to monitor anevaporation state by an optical means so that evaporation states of twoor more elements can be evaluated independently, and exhibits highadaptability to the present invention.

1. A method for manufacturing a thin film, the thin film containing afirst thin film material and a second thin film material, in which thethin film is manufactured on a surface to be vapor-deposited by vacuumvapor deposition, wherein the first thin film material and the secondthin film material are evaporated by heating using an electron beamheating method and a resistance heating method, respectively, and anelectron beam to be used to heat the first thin film material is passedthrough a vapor stream of the second thin film material.
 2. The methodaccording to claim 1, wherein a reactive gas is introduced in a portionon the surface to be vapor-deposited in which the thin film is to beformed.
 3. The method according to claim 1, wherein a bias voltage isapplied to the surface to be vapor-deposited.
 4. The method according toclaim 1, wherein the first thin film material is Co, and the second thinfilm material is Li.
 5. An apparatus for manufacturing a thin film,comprising: an electron beam evaporation source that is arranged so asto face a surface to be vapor-deposited and contains a first thin filmmaterial; an electron beam source that emits an electron beam to be usedto evaporate the first thin film material by heating using an electronbeam heating method; and a resistance heating evaporation source that isarranged so as to face the surface to be vapor-deposited and evaporatesa. second thin film material by heating using a resistance heatingmethod, wherein the electron beam evaporation source, the electron beamsource and the resistance heating evaporation source are arranged sothat the electron beam passes through a vapor stream of the second thinfilm material.
 6. The apparatus according to claim 5, wherein theelectron beam evaporation source, the resistance heating evaporationsource and the electron beam source are arranged in this order.
 7. Theapparatus according to claim 5, further comprising a nozzle forintroducing a reactive gas in a portion on the surface to bevapor-deposited in which the thin film is to be formed.
 8. The apparatusaccording to claim 5, further comprising a bias device for applying abias voltage to the surface to be vapor-deposited.
 9. The apparatusaccording to claim 5, wherein the electron beam evaporation source, theelectron beam source and the resistance heating evaporation source arearranged substantially on the same plane.